1. Field of the Invention
The present invention relates to a magnetoresistive element often utilized in a magnetic recording medium drive such as a magnetic disk drive as well as a magnetic tape drive. In particular, the invention relates to a current-perpendicular-to-the-plane (CPP) structure magnetoresistive element comprising: the lower portion of a magnetoresistive film extending over the surface of a lower magnetic pole layer by a first lateral width; the upper portion of the magnetoresistive film extending over the surface of the lower portion by a second lateral width smaller than the first lateral width; and an upper magnetic pole layer contacting the upper portion of the magnetoresistive film, and a method of making the same.
2. Description of the Prior Art
A magnetoresistive film, such as a spin valve film, usually includes a pinning antiferromagnetic layer, a pinned ferromagnetic layer and a non-magnetic intermediate layer for the lower portion of the magnetoresistive film. The magnetoresistive film further includes the upper portion including a free ferromagnetic layer extending over the surface of the non-magnetic intermediate layer. In the technical field of CPP structure magnetoresistive elements, the upper portion is often reduced in the width in the lateral direction of a recording track as compared with the lower portion in the magnetoresistive film. The upper portion is interposed between insulator layers on the lower portion. The insulator layers serves to establish a narrower path for electric current between the lower portion of the magnetoresistive film and the upper magnetic pole layer. The substantial width in the lateral direction can be reduced in the magnetoresistive film.
The upper portion is carved out of a layered material on the lower portion in the magnetoresistive film. A pair of domain control magnetic layers, namely, biasing hard magnetic layers are subjected to an etching process on the laterally opposite ends of the upper portion of the magnetoresistive film. The level of the domain control magnetic layers gets lowered to the level of the upper surface of the lower portion. The upper portion of the magnetoresistive film gets completely out of the space between the domain control magnetic layers. The longitudinal biasing magnetic field induced between the domain control magnetic layers cannot act enough over the free ferromagnetic layer in the upper portion of the magnetoresistive film. The Barkhausen noise cannot be reduced enough.